Field of the Invention
This invention relates to durable epoxy (meth)acrylic polymers with oxirane-containing terminal groups; to processes for preparing beta-ketoesters and beta-sulfonylesters from silylketene acetals; and to block and chain-extended polymers prepared therewith.
Background
Epoxy resins are widely used today in surface coatings, adhesives, castings, laminates, and encapsulation of electronic parts. Most of these epoxy resins are prepared by the reaction of 2,2-bis(4'-hydroxyphenyl)propane [bisphenol A] and epichlorohydrin. This generates a polymer with a backbone composed of ether links between bisphenol A structures and hydroxy propylene moieties. There is also one epoxy group (oxirane) at each end of the polymer backbone. These resins can be cured by reacting their epoxy groups with crosslinking agents, such as anhydrides, amines, and acids. When cured, the epoxides have good tensile strengths, excellent electrical insulating properties, and have outstanding adhesion to many surfaces.
However, a major weakness of these conventional epoxy resins is their poor outdoor durability. The ether links in their backbone as well as the aromatic rings lead to poor UV and oxidative stability. Because of this limitation, these epoxy resins cannot be used in systems that require long term outdoor exposure.
Previously, two approaches have been taken to make durable epoxides. One involves the synthesis and use of low molecular weight cyclic or acyclic diepoxides and the other involves the synthesis and use of copolymers of glycidyl methacrylate (GMA). Both of these approaches, although they generate epoxides that are more durable than bisphenol A based resins, have significant deficiencies. The cyclic-type of epoxides are not polymers and have only very low molecular weight segments binding the two epoxy groups. These materials tend not to have the superior physical properties of conventional epoxides. The systems based on random copolymers of GMA do not have the controlled placement of the epoxy groups. That is, these copolymers have the epoxy groups distributed randomly along the entire backbone of the methacrylate chain. The placement of the epoxy groups at the end of the polymer chain, as seen in bisphenol A epoxides, imparts important properties such as toughness. The random placement of the epoxy groups lowers final properties.
The bisphenol A-based epoxides are well known and are items of commerce (e.g., the Epon resins from Shell and the family of DER epoxides from Dow). The cyclic epoxides have also been commercially available (e.g. Union Carbide's ERL-4221, a cycloaliphatic diepoxide).
Methacrylate copolymers that use randomly distributed GMA have been used in the coatings industry (U.S. Pat. Nos. 3,817,946; 4,027,066; 3,730,930; 4,346,144). However, no patents or publications have been identified that report ABA triblock methacrylate polymers with GMA in the A segments.
Patents and publications concerning Group Transfer Polymerization (GTP) disclose the ability to make block structures using that process. However, none of these discloses the epoxy triblock structure, nor the advantages of that structure as a durable epoxy resin. For a detailed discussion of GTP see Webster et al., "Group Transfer Polymerization--A New and Versatile Kind of Addition Polymerization", J. Am. Chem. Soc. 105, 5706 (1983); and U.S. Pat. Nos. 4,414,372; 4,417,034; 4,508,880; 4,524,196; 4,581,428; 4,588,795; 4,598,161; 4,605,716; 4,622,372; and 4,656,233; and commonly assigned U.S. patent application Ser. Nos. 660,588 filed Oct. 18, 1984; 673,926 filed Nov. 21, 1984; and 004,831 filed Jan. 13, 1987. The disclosures of these patents and applications are hereby incorporated by reference. More specifically, these patents and applications disclose processes for polymerizing an acrylic or maleimide monomer to a "living" polymer in the presence of:
(i) an initiator having at least one initiating site and which is a tetracoordinate organo (Si, Sn or Ge) compound, including such compound having at least one oxygen, nitrogen or sulfur atom attached to Si; and
(ii) a co-catalyst which is a source of fluoride, bifluoride, cyanide or azide ions or a suitable Lewis acid, Lewis base or selected oxyanion.
The aforesaid patents and applications also disclose capping of "living" silylketene acetal groups with agents containing capping functions such as --CHO, --C(O)--, --NCO, --Br, --Cl and --TiCl.sub.3.
In GTP processes, the polymer produced is "living" in that the polymerization is characterized by the presence, in the growing and in the grown polymer, of a moiety containing the aforesaid metal at "living" ends and the activating substituent or diradical, or a tautomer thereof, at "nonliving" ends of the polymer.
Monomers which are useful in GTP are of the formula CH.sub.2 .dbd.C(Y)X wherein:
X is --CN, --CH.dbd.CHC(O)X' or --C(O)X'; PA1 Y is --H, --CH.sub.3, --CN or --CO.sub.2 R, provided, however, when X is --CH.dbd.CHC(O)X', Y is --H or --CH.sub.3 ; PA1 X' is --OSi(R.sup.1).sub.3, --R, --OR or --NR'R"; PA1 each R.sup.1, independently, is H or a hydrocarbyl radical which is an aliphatic, alicyclic, aromatic or mixed aliphatic-aromatic radical containing up to 20 carbon atoms, provided that least one R.sup.1 group is not H; PA1 R is a hydrocarbyl radical which is an aliphatic, alicyclic, aromatic or mixed aliphatic-aromatic radical containing up to 20 carbon atoms, or a polymeric radical containing at least 20 carbon atoms, any of said radicals optionally containing one or more ether oxygen atoms within aliphatic segments thereof, optionally containing one or more functional substituents that are unreactive under polymerizing conditions, and optionally containing one or more reactive substituents of the formula --Z'(O)C--C(Y.sup.1).dbd.CH.sub.2 wherein Y.sup.1 is H or CH.sub.3 and Z' is O or NR'; and PA1 each of R' and R" is independently selected from C.sub.1-4 alkyl. PA1 R.sup.1 is as defined above; PA1 Z is an activating substituent selected from the group consisting of ##STR1## m is 2, 3 or 4; PA1 n is 3, 4 or 5; PA1 M is Si, Sn or Ge, provided, however, when Z is ##STR2## and mixtures PA1 thereof, wherein R.sup.2, R.sup.3, X', Z', m and n are as defined above provided however when Z.sup.2 is ##STR3## if PA1 Z is ##STR4## and
Initiators which are useful in GTP include the silicon-containing initiators of U.S. Pat. Nos. 4,414,372; 4,524,196; 4,417,034; 4,508,880; 4,581,428; and 4,656,233, supra, and application Ser. Nos. 660,588 and 673,926, supra. Initiators which are preferred for use herein are of the formula selected from (R.sup.1).sub.3 MZ, (R.sup.1).sub.2 M(Z.sup.1).sub.2 and O[M(R.sup.1).sub.2 X.sup.1 ].sub.2 wherein:
(c) X' and either R.sup.2 or R.sup.3 taken together are ##STR5## if Z is ##STR6##
R. A. Olofson and J. Cuomo, Tetrahedron Lett., 21, 819 (1980) disclose fluoride ion catalyzed O-acylation of silyl enol ethers with compounds of the type RXC(O)F where X is O, NR' or a single bond, R is a cyclic or acyclic aliphatic radical and R' is methyl or, together with R, morpholino. C-acylation of silyl enol ethers is not reported.
U.S. Pat. No. 4,482,729 discloses reactions of non-polymeric fluorine-containing silylketene acetals such as CF.sub.3 CH.dbd.C(OSi(CH.sub.3).sub.3)OCH.sub.3, including reaction with a propionyl chloride, to form the alpha-trifluoromethyl-beta-ketoester CH.sub.3 CH.sub.2 C(O)CH(CF.sub.3)CO.sub.2 CH.sub.3. Electron-withdrawing substituents such as --COOR attached to the double bond of silylketene acetals are known to promote reaction with acyl chlorides and anhydrides; --CH.sub.3 is strongly electron-withdrawing.
Japanese Patent Application No. 53/034-719 discloses the preparation of alpha-hydroxysuccinic acid esters by reaction of non-polymeric silylketene acetals with alpha-ketocarboxylic esters in the presence of a Lewis acid catalyst.
E. Colvin, "Silicon in Organic Synthesis", page 234, Butterworths, Boston (1981); and M. W. Rathke and D. F. Sullivan, Tetrahedron Lett., 1297 (1973) show that even with amine promoters, acylation of silylketene acetals (SKA) does not occur with acyl chlorides when the SKA contains two .alpha.-substituents. Polymerizing methacrylate chain ends have two such substituents. These references further disclose that a stoichiometric amount of amine is required even when less than two .alpha.-substituents are present.
Acylation of non-polymeric silyl enol ethers is well known. For example, R. Noyori et al., Tet., 37, 3899 (1981) disclose the acylation of silyl enol ethers in the presence of trimethylsilyl triflate as the (Lewis acid) catalyst. R. E. Tirpak et al., J. Org. Chem., 47, 5099 (1982) disclose acylation of silyl enol ethers with acyl chlorides in the presence of Lewis acid promoters. E. P. Kramarova et al., J. Gen. Chem. USSR, 43, 1843 (1973); ibid., 45, 469 (1975) disclose C-acylation, usually, of silyl enol ethers by reaction with acyl chlorides or anhydrides; the former require catalytic amounts of mercuric chloride; the latter contain activating alpha-halogen atoms.
G. S. Burlachenko et al., J. Gen. Chem., USSR, 43, 1708 (1973) disclose the reaction of alkyl silylketene acetals with acetyl chloride or triethylsilylacetyl chloride. The reaction produces alkylsilyl derivatives of acetoacetic enol esters, e.g. CH.sub.3 COCl+2CH.sub.2 .dbd.C(OCH.sub.3)OSi(C.sub.2 H.sub.5).sub.3 .fwdarw.CH.sub.3 C(OSi[C.sub.2 H.sub.5 ].sub.3).dbd.CHCO.sub.2 CH.sub.3.
A. Wissner, J. Org. Chem., 44(25), 4617 (1979) discloses a similar reaction to that of Burlachenko et al., and further shows that acid-catalyzed hydrolysis of the enol ester provides a beta-ketoester. The reactions of Burlachenko et al., and Wissner require that the silylketene acetal contain an olefinic hydrogen atom, which is released during the reaction as HCl.
G. Rousseau et al., Tetrahedron Lett., 26(35), 4191 (1985) disclose the C-acylation of non-polymeric silylketene acetals with acryloyl and mono-substituted acryloyl chlorides to form beta-ketoesters. The reaction is catalyzed by Lewis acids such as zinc bromide. Mainly, delta-diesters or delta-esteracids are produced without Lewis acid catalysis when alpha, beta-unsaturated acyl chlorides are used, the reaction involving addition to carbon-carbon double bonds, not to carbonyl.
The acylating and sulfonylating agents and silylketene acetals employed in the invention which will be described in greater detail hereinbelow are known or obvious compounds. The polymeric silylketene acetal reactants are "living" polymers prepared by Group Transfer Polymerization, supra.
The invention which will be described in greater detail hereinbelow also is concerned with ABA triblock polymers that have glycidyl methacrylate (GMA) as the A segments and standard (meth)acrylate monomers as the B segment. These methacrylate triblock polymers have now been synthesized with epoxy groups located only at the ends of the polymer chain. Because their backbone is a (meth)acrylate (meaning acrylate and/or methacrylate) structure, these epoxy resins should be significantly more durable than conventional bisphenol A based epoxides. These new polymers should have better final properties than the cyclic epoxides because the backbone is polymeric in nature. They should be better than conventional GMA polymers that have a random distribution of epoxy groups because all of the epoxy groups are now located at the end of the chains, similar to bisphenol A epoxides.